Many systems and techniques exist for detecting appli- cation failures. However, previously known generic failure detection solutions are only of limited use for Java applications because they do not take into consideration the specifcs of the Java language and the Java execution environment. In this article, we present the application- independent Java Application Supervisor (JAS). JAS can automati- cally detect, log, and resolve avariety of execution problems and fail- ures in Java applications. In most cases, JAS requires neither modi- fications nor access to the source code of the supervised application. A set of simple user-specfied policies guides the failure detection, log- ging, and recovery process in JAS. A JAS configuration manager au- tomatically generates default policies from the bytecode of an applica- tion. The user can modify these default policies as needed. Our ex- perimental studies show that JAS typically incurs little execution time and memory overhead for the target application. We describe an ex- periment with a Web proxy that exhibits reliability and performance problems under heavy load and demonstrate an increase in the rate of successful requests to the server by almost 33% and a decrease in the average request processing time by approximately 22% when using JAS. Index Terms: Availability, Failure Detection, Java, Logging, Object Persistence, Policies, Recovery, Server.